1. Technical Field
The present invention belongs to the technical field of digital streams and application-synchronized playback.
2. Background Art
Application-synchronized playback is technology for playing digital streams while at the same time running Java (registered trademark) applications in a playback apparatus or the like for playing video, and belongs to a technical field that will attract a great deal of attention in consumer device manufacturing from now on. Applications and digital streams for synchronizing are associated with one another in units of playback called titles”. The following describes a conventional playback apparatus. A conventional playback apparatus is constituted from a virtual filesystem unit, a module manager, a playback unit, and a platform unit.
The virtual filesystem unit manages a plurality of recording media accessible by the playback apparatus such as optical recording media (e.g. DVD-ROM, BD-ROM, the latter of which is described later by way of example) and magnetic recording media (e.g. hard disk), and generates package information integrally showing the recorded content of these recording media.
Each piece of package information, called a virtual package, is submitted in the playback/execution of digital streams and application programs (hereinafter simply “applications”) recorded on these recording media just as if they were actually recorded in a single package.
The module manager selects one of a plurality of titles as a current title.
The playback unit plays a digital stream (i.e. recorded on an optical or magnetic recording medium) constituting the current title from digital streams shown by the package information.
The platform unit runs an application (i.e. recorded on an optical or magnetic recording medium) constituting the current title from applications shown by the package information.
According to the above structure, digital streams and applications recorded on different recording media such as BD-ROM and hard disk can be treated as a single (virtual) package, and the playback apparatus is able to realize playback controls in units of titles.
Titles in the above structure target not only digital streams recorded on BD-ROM for playback but also digital streams recorded on hard disk. Since hard disk is a rewritable recording medium, the compositional elements of a title may possibly be replaced partway through playback in cases such as when package information is newly generated using a newly acquired digital stream.
Such a replacement is largely thought to bring about situations that are difficult to restore such as video blackout during playback resulting from abnormal operation of the playback unit.
The replacement of the playback object partway through playback can be anticipated if the playback unit in the playback apparatus sequentially checks the sameness of elements such as streams and playback control information targeted for playback. However, given the diverse types of information that require checking, this places a great burden on the playback unit.
To be absolutely sure of the device's stable operation, it is desirable to reboot the device itself when there has been a change in the recorded content on hard disk, as you would when installing software. However, given that rebooting the device takes anywhere from a few seconds to a few minutes processing time, this is not something that the user undertakes lightly.